i think D1 football should not be an automatic disqualifier for future BE membership.
For example, UMass would be a good addition. They can play basketball in the BE and keep their football in the MAC. No major conference is EVER going to target them. Every school in the MAC, Conf USA, WAC, Mountain West, would have to be taken before UMass goes to a major conference.
Dayton is a school that I would have chosen over Butler, but I would rather look elsewhere at this point. It might be a good idea to see what happens with BYU over the next couple of years, and if the B-12 or ACC dont take them, their football may be looking at eternal independence, in which case their basketball program might be a good BE target.